Endoprosthetic devices commonly referred to as a "stents" generally comprise a rigid structural member which may be implanted within an anatomical structure to reinforce or support a portion of the anatomical structure which has become occluded, weakened, compressed or otherwise affected by pathology. Stent devices of various configuration have heretofore been successfully utilized to reinforce or dilate numerous types of anatomical structures, including blood vessels, urogenital passageways and bile ducts.
In cardiovascular applications, endovascular stents are typically inserted into a blood vessel to dilate areas of the vessel which have become occluded by atherosclerotic plaque or constricted by an adjacent tumor. Insertion and endovascular deployment of the stent may be accomplished either intraoperatively through an open incision or percutaneously through a transluminally positioned catheter or similar introducer apparatus.
Endovascular stents of the prior art have typically fallen into two general categories of construction. The first category of endovascular stent is the self-expanding stent formed of spring metal or similar material and deployable through the lumen of a tubular catheter or sleeve such that, when the self-expanding stent is advanced out of the distal end of the catheter or sleeve, it will automatically expand so as to exert pressure against the surrounding blood vessel wall. The second category of stent is the pressure-expandable stent. Pressure-expandable stents are typically formed of rigid, pre-set material and may be deployed on an inflatable balloon or other expanding member such that, upon inflation of the balloon or expansion of the deployer, the stent will be radially enlarged to a desired diameter such that the stent becomes positioned against the surrounding blood vessel wall.
Self-expanding endovascular stents of the prior art include those described in U.S. Pat. Nos. 4,580,568 (GIANTURCO); and 4,830,003, (WOLFF, et al.) and foreign patent publication no. EP 183372A.
Pressure-expandable endovascular stents of the prior art include those described in U.S. Pat. Nos. 5,135,336 (HULSTEAD); 4,733,685 (PALMANTZ); 4,922,905 (STRECKER); 4,950,227 (SAVIN, et al.); 5,041,126 (GIANTURCO); 5,108,416 (RYAN, et al.) 5,161,547 (TOWER) (and foreign patent publications nos. EP-378151A; and EP246998A.
In clinical practice, the utilization of endovascular stent devices has generally been associated with an incidence of thromboembolic complications. Such thromboembolic complications are believed to result, at least in part, due to a) disruption of laminar blood flow by the stent itself and/or b) non-biocompatibility of the stent material.
In view of the clinical incidence of thromboembolic complications experienced with endovascular stent devices of the prior art, there remains a need for newly designed endovascular stent devices which promote non-turbulent laminar blood flow through the lumen of the blood vessel and which minimize the surface area of stent-host interface so as to minimize potential complications due to non-biocompatibility of the stent.